1910] RIDDLE—STEREOCAULON 295 
TOMENTUM 
CEPHALODIA 
Absent | Medium | Abundant 
Tomentosum type.... ° 16 34 
Paschale type....... 24 19 ° 
These tables show conclusively the extent to which S. paschale and S. 
tomentosum intergrade. ey show also the confusion introduced by taking 
the presence of tomentum alone as a criterion, for, as is shown in the second 
table, out of 93 specimens 35 were intermediate in the amount of tomentum. 
With such intergrading, complete correlation of characters is not to be expected. 
But the tables show that the types of cephalodia are correlated to a pees 
_ degree with the two characters that have been recognized as of chief importa 
in separating these two species. The results of the statistical study, Suche 
support very strongly the te that the cephalodia, when present, are 
of great taxonomic value. Yet taking all available characters into considera- 
tion, there are still specimens which cannot be placed absolutely under either 
of these.species, but exhibit characters of both. And this must necessarily 
be so on account of the fact that in nature S. paschale and S. tomentosum 
Seely form a continuous, variable series, the forms that we recognize as 
“typical” being merely the two extremes of this se 
the numerous forms of S. paschale which em been distinguished by 
European authors only one seems to be of sufficient importance in North 
America to receive separate treatment. This is 5 
4a. STEREOCAULON PASCHALE var. CONGLOMERATUM Fries. 
Fries Sched. Crit. ad Lich. Suec. 3:20. 1824. 
Podetia much branched, forming compact cushions which are 
closely adnate to the substratum, squamules more granular and 
crowded than in the type; usually sterile-—Growing on rocks. 
SPECIMENS EXAMINED 
UROPE: Fries Lich. Suec. no. 89; Hepp Lich. Eu. no. 304; Sweden, Are- 
— (Tuck). 
New HampsHrre: Mt. Monadnock, W. G. Farlow July 1, 1896 (H); 
_ Alton Bay, C. J. Sprague (BSNH). 
VERMONT: Mt. Ascutney, R. H. Howe, Jr., Aug. 25, 1909 (Th). 
Massacuuserrs: Annisquam, Clara E. Cuntnines 1892 > (CEC): Wellesley, 
Clara E. Cummings Dec. 1884 (CEC); L. W. Riddle Jan. 1908 (R). 
This is a reduced form of S. paschale, occurring either at low altitudes or 
on rocks with extreme exposure. It passes into the laxer, more typical form 
by insensible gradations. The only other species with which this variety may 
